What are heart rhythm problems (arrhythmias)?

An arrhythmia, or heart rhythm disturbance, is a change in the regular beat of the heart. The heart is divided into four chambers: two atria on top and two ventricles on the bottom. Arrhythmias are classified by their location as ventricular or atrial (sometimes called supraventricular meaning above the ventricle) and whether they slow the heart rate: bradycardia(heart rate less then 60 beats per minute); or speed it up: tachycardia (heart rate more than 100 beats per minute).

Are arrhythmias serious?

Heart rhythm disturbances can occur in people without heart disease and in many cases they are harmless. However, some heart rhythm disturbances affect the heart’s ability to pump blood around the body. In 2002, arrhythmias caused nearly 38,000 deaths. Arrhythmias can lead to sudden cardiac death, or SCD, often brought on by cardiac arrest, when the heart abruptly stops beating. If the heart is not restarted immediately with an electric shock ( defibrillation), death can occur. Most cases of SCD occur in people with heart disease, and SCD accounts for half the deaths from cardiovascular disease. Each year, three to four times more men experience SCD than women, but the gender gap closes with older age.

Who should take medication for heart rhythm problems?

This section will focus on the use of antiarrhythmic medications in people with heart disease (fatty plaque buildup in the arteries of the heart), particularly heart attack patients. Heart rhythm disturbances are common early after heart attack symptoms develop. Previously, antiarrhythmic medications were given to heart attack patients to help prevent heart rhythm problems from occurring in the first place. Now it is known that in most cases, these drugs do more harm than good when used preventively (beta blockers are the exception).

Currently, heart rhythm medications are reserved for occasionally treating serious heart rhythm problems when they arise. Implantable cardioverter defibrillators (ICDs) and pacemakers are safer and better than drugs for the long-term treatment of serious heart rhythm problems. Some people with ICDs also take antiarrhythmic medication to reduce the likelihood of shocks.

There are four classes of antiarrhythmic medications categorized according to how they affect heart rhythm disturbances. A fifth group exists for drugs that do not fit into the other categories. Some medications have properties from more than one class (e.g., amiodarone). The heartbeat is controlled by an electrical conduction system that sends electrical charges to the heart muscle causing it to expand and contract. Antiarrhythmics work by slowing down the electrical signals in the heart so the heart can resume a regular rhythm.

Class I antiarrhythmics are sodium channel blockers that block the flow of sodium to the heart. They are further divided into three subclasses (IA, IB, and IC).

Class II antiarrhythmics are beta blockers that block the stimulating effect of adrenaline on the heart.

Class III antiarrhythmics block potassium channel blockers that block the flow of potassium to the heart.

Class IV antiarrhythmics are calcium channel blockers that block the flow of calcium to the heart.

This “class” is made up of two drugs, digoxin and adenosine. Digoxin and adenosine slow the conduction of electrical impulses through the AV node – a kind of junction box for the electrical signal between the upper and lower chambers of the heart.

Class I – Sodium Channel Blockers

Do sodium channel blockers prevent heart rhythm problems?

In the past, class I antiarrhythmics were routinely given to heart attack patients to prevent heart rhythm disturbances. However, many studies now show that these medications are not beneficial and actually increase the risk of dying because they often triggerheart rhythm disturbances. In a combined analysis of 138 studies involving 98,000 heart attack survivors, men and women treated with class I antiarrhythmics had a significantly higher risk of dying compared with patients given dummy pills. For these reasons, class I medications are no longer routinely prescribed to heart attack patients. Some of these medications may be injected through an IV line to treat continuing arrhythmias in hospitalized heart attack patients.

Prescribed Class I Antiarrhythmics

Class I Antiarrhythmics – Sodium Channel Blockers
(check with manufacturer for specific information on each drug)

Cardiogenic shock (the heart muscle is so damaged it cannot pump properly, causing a shock-like state)

Second- or third-degree heart block (the electrical signals between the upper and lower chambers of the heart are impaired)

Lupus

Torsade de pointes (a type of rapid heart beat that may be caused by a birth defect or by some medications)

Common side effects

Arrhythmias (which can be fatal, particularly in people who have heart disease), digestive upset, dizziness, lightheadedness, tremor, retention of urine, and dry mouth

Pregnancy/nursing

The safety of these medications during pregnancy is unknown

Women who are nursing should not use these medications; if the treatment is essential, then nursing should be discontinued

Class II – Beta-Blockers

Do beta blockers prevent heart rhythm problems?

Class II antiarrhythmics, beta blockers, are the only heart rhythm medications used to prevent heart rhythm problems from occurring in the first place. In people who have had a heart attack, beta blockers reduce the risk of dying, having another heart attack, or experiencing sudden cardiac death. The risk of dying is reduced by 25% to 40%, and sudden cardiac death specifically is lowered by 30% to 45%. This survival benefit continues for up to 6 years after the heart attack. It is not fully understood how beta blockers prevent heart rhythm problems: they may have a direct antiarrhythmic effect, or their ability to widen arteries and increase blood flow to the heart may indirectly lower the risk of certain heart rhythm disturbances, particularly ventricular tachyarrhythmia (a rapid irregular heart beat originating in the lower chambers of the heart).

You may be given beta blockers shortly after heart attack symptoms begin. These medications should not be used in some patients including those with a slow heart rate or signs of heart failure, so doctors often wait 24 to 48 hours to rule out these conditions before giving patients beta blockers. A combined analysis of studies involving nearly 54,000 men and women who had a heart attack found that taking beta-blockers for up to four years reduced the chances of dying by 23%. If you had a heart attack, you will likely continue to take beta blockers for the rest of your life.

Pregnant women should not take atenolol because it can harm the fetus. The safety of the other beta blockers during pregnancy is not known

Women who are nursing should not use beta blockers; if the treatment is essential, then nursing should be discontinued.

Are beta blockers underprescribed?

Many heart attack patients who are eligible for beta blockers do not receive prescriptions, particularly women and the elderly. A 1999 study of more than 15,000 patients (nearly half were women) found that among the 5,453 heart attack patients older than 66 years of age who were eligible for beta blockers, women were significantly less likely than men to be prescribed them at hospital discharge. More recent studies note that people who have had a heart attack are more likely to receive recommended medications, including beta blockers, than in previous years; however, the gender gap remains.

Class III – Potassium Channel Blockers

Are potassium channel blockers beneficial?

Unlike some of the other heart rhythm drugs, class III anti-arrhythmics do not increase the risk of dying early in men or women with heart disease. A version of sotalol increased the risk of dying from heart rhythm disturbances when used to prevent arrhythmias in heart attack patients. This risk was higher for women than men. That formulation of sotalol is no longer used. The current version of sotalol (Betapace) does not increase the risk of dying from heart rhythm problems when given to people with heart disease. Class III antiarrhythmic medications are not used to prevent heart rhythm problems because it is not clear whether they are beneficial in that situation. These medications may be used to treat arrhythmias in men and women with heart disease who are taking beta blockers but continue to experience heart rhythm problems, including atrial fibrillation. Atrial fibrillation is a rapid, disordered contraction of the heart muscles whereby the heart flutters in an uncontrolled manner.

Treatment of life-threatening recurrent ventricular fibrillation and recurrent ventricular tachycardiathat affects blood flow to the heart when these have not responded to available doses of other antiarrhythmic medications

Maintenance of normal heart rhythm in patients with atrial fibrillation/flutter for more than 1 week that was corrected to normal heart rhythm; should be reserved for patients with symptoms

Correction of atrial fibrillation/flutter to normal heart rhythm

You should not take this medication

When episodes of slow heart rate have caused fainting

If you have been diagnosed with:

Cardiogenic shock (the heart muscle is so damaged it cannot pump properly, causing a shock-like state)

Second- and third-degree heart block (the electrical signals between the upper and lower chambers of the heart are impaired)

Abnormally slow heartbeat

Uncontrolled congestive heart failure

Long QT syndrome the electrical activation and deactivation of the ventricles takes longer than usual

Asthma

Common side effects

Arrhythmias, scarring in the lungs (pulmonaryfibrosis), and low blood pressure

Pregnancy/nursing

Pregnant women should not take amiodarone because it can harm the fetus

Women who are nursing should not use these medications; if the treatment is essential, then nursing should be discontinued

Choice of Medication

Amiodarone (Pacerone or Cordarone) is better than sotalol for correcting heart rhythm disturbances; however, it has a higher risk of very serious side effects. In two major studies, many heart attack patients prescribed amiodarone stopped taking it because of side effects, including serious lung and liver problems. In one study of elderly heart attack patients with atrial fibrillation, women treated with amiodarone had a higher risk of developing a slow irregular heartbeat (bradyarrhythmia) requiring permanent pacemaker than men taking amiodarone. Because of these risks, sotalol is generally the first choice. Dofetilide (Tikosyn) is newer and has not been studied as much as the other class III antiarrhythmics. Both amiodarone and dofetilide have been shown to benefit men and women with heart failure. Sotalol and dofetilide may trigger a potentially dangerous rapid heart beat (torsade de pointes), particularly in women.

Amiodarone or sotalol may also be given to people with ICDs to reduce the number of shocks.

Class IV – Calcium Channel Blockers

Are calcium channel blockers beneficial?

In general, class IV agents, (calcium channel blockers, or CCBs), do not reduce the risk of dying in people who have had a heart attack or have unstable angina (chest pain), and in some cases they do more harm than good. For this reason they are no longer routinely prescribed after a heart attack. There are two types of CCBs: the dihydropyridines (such as amlodipine and nifedipine) are harmful in heart attack patients. The other type, non-dihydropyridines(such as verapamil and diltiazem) may be harmful in patients who have chronic heart failure, a very slow irregular heartbeat (bradyarrhythmia), or lung problems. In heart attack patients who do not have these conditions, verapamil (Covera or Verelan) reduces the risk of dying or suffering further heart problems, and diltiazem (Cardizem or Tiazac) lowers the risk of having another heart attack. These particular CCBs may be used for the short-term treatment of arrhythmias in heart attack patients who cannot take beta blockers. Many CCBs come in a short-acting and a long-acting (sustained release) form. Short-acting CCBs increase the risk of heart attack and stroke when used over an extended period.

Second- or third-degree heart block (the electrical signals between the upper and lower chambers of the heart are impaired) unless pacemaker present

Sick sinus syndrome (the heart’s natural pacemaker, the sinus node, does not work properly) except when a pacemaker is present

Low blood pressure

Patients with cardiogenic shock (the heart muscle is so damaged it cannot pump properly, causing a shock-like state), severe damage to the left side of the heart, or atrial fibrillation or flutter associated with Wolff-Parkinson-White syndrome should not take verapamil

Common side effects

Headaches and swelling of the ankles

Verapamil can cause constipation and excessive slowing of the heartbeat

Pregnancy/nursing

The safety of these medications during pregnancy is unknown

Women who are nursing should not use calcium channel blockers; if the treatment is essential, then nursing should be discontinued

Class V – Miscellaneous

Are class V antiarrhythmics beneficial?

In people with heart disease, the class V antiarrhythmics are used to treat certain heart rhythm disturbances affecting the upper chambers of the heart (the atria). They are not used to prevent arrhythmia. These antiarrhyhmics should be used with caution since men and women taking digoxin (Lanoxin) after having a heart attack have an increased risk of dying early. Digoxin may be used to relieve symptoms of atrial fibrillation (see below) in people with heart failure or severe damage to the left side of the heart.

Prescribed Class V antiarrhythmics

Miscellaneous Antiarrhythmics
(check with manufacturer for specific information on each drug)

Generic

Adenosine

Digoxin

Brand

Adenocard IV

Lanoxin

Administration

Oral, intravenous

Indications

To restore normal heart rhythm in people with occasional supraventricular tachycardia including that associated with Wolff-Parkinson-White syndrome

Treatment of mild to moderate heart failure

Control of chronic atrial fibrillation

You should not be treated with these medications

If you have been diagnosed with:

Second- or third-degree heart block (the electrical signals between the upper and lower chambers of the heart are impaired) except when a pacemaker is present

Women who are nursing should not take digoxin; if the treatment is essential, then nursing should be discontinued

What are the risks of heart rhythm drugs?

With the exception of beta blockers, the benefits of antiarrhythmic medications must be carefully balanced against the risk of triggering a fatal heart rhythm disturbance. These medications are generally reserved for people with life-threatening arrhythmias. Therapy is usually initiated in the hospital where you can be monitored.

Women taking antiarrhythmic medications have a higher risk than men of developing the life-threatening rapid heartbeat torsade de pointes (TdP), particularly with class IA medications and sotalol (Betapace), a class III antiarrhythmic. Women have a higher risk of TdP to begin with because the time between electrical activation and deactivation of the lower chambers of the heart is longer for women than men (called the QT interval in reference to the pattern produced on the ECG). Two-thirds of heart medication-induced TdP cases occur in women, and it is estimated that TdP accounts for 5% of the 300,000 sudden cardiac deaths each year.

Magnesium

Low blood levels of magnesium increase the risk of heart rhythm disturbances. Older studies suggested that heart attack patients benefited from intravenous injections of magnesium. Contemporary studies where most heart attack patients are treated with balloon angioplasty or clot busting drugs do not show a benefit for IV magnesium in men or women. IV magnesium may help treat some life-threatening ventricular arrhythmias, including torsade de pointes (see Risks). It is not known whether dietary magnesium or supplements lower the risk of developing heart rhythm problems.

Medication for Common Rhythm Problems

Ventricular Fibrillation

Rapid, disordered contraction of the heart muscles whereby the heart flutters in an uncontrolled manner (fibrillation) is the most serious type of arrhythmia.Ventricular fibrillation (VF) is thought to be responsible for many of the 335,000 sudden cardiac deaths reported each year. Because reduced blood flow to the heart often causes or contributes to this heart rhythm disturbance, VF is a concern for heart attack patients.

Most cases of VF occur in the first four hours after a heart attack. The risk of dying from this heart rhythm disturbance has declined with improved heart attack treatments, but VF can cause death in the first day after a heart attack. Heart attack patients used to be given the class I antiarrhythmic lidocaine to prevent VF, but this is no longer done because there is no clear evidence that it reduces the risk of dying and some evidence suggest that it may be harmful. Intravenous beta blockers help prevent ventricular fibrillation early after a heart attack and are given to patients who can tolerate beta blockers. When VF occurs, it is treated with cardioversion; an electric shock is delivered to the heart using paddles placed on the chest (as commonly seen on television medical dramas). VF that is not corrected by shock may be treated with amiodarone, a class III antiarrhythmic. If VF occurs more than 2 days after a heart attack, you may need to have an ICD implanted.

Ventricular Tachycardia

Ventricular tachycardia (VT) is a rapid heartbeat affecting the lower chambers of the heart. Most cases of VT occur within the first 48 hours after a heart attack. Often, this rhythm disturbance will correct itself without needing treatment. VT that does not impair blood flow to the heart may be treated with medication, preferably amiodarone. VT that impairs blood flow to the heart requires electric shock treatment (cardioversion). People who experience VT that impairs blood flow to the heart more than 2 days after a heart attack have a poor prognosis and may need to have an ICD implanted.

Atrial Fibrillation

The most common cardiac arrhythmia is atrial fibrillation (AF), a rapid, disordered contraction of the heart muscles whereby the heart flutters in an uncontrolled manner. Atrial fibrillation affects 2.2 million people in the US, and approximately 55% of people discharged with a diagnosis of AF are women. Heart attack patients who experience AF have a higher risk of dying or experiencing other heart problems both in the hospital and in the long-term than heart attack patients who do not suffer this heart rhythm disturbance. When medical therapy is required, intravenous beta blockers slow the heart rate. The calcium channel blockers verapamil (Covera or Verelan) and diltiazem (Cardizem or Tiazac) may be used for controlling the rapid heart rate in the short-term in patients who cannot take beta blockers; however, calcium channel blockers increase the risk of dying after a heart attack when used for longer periods of time. Digoxin (Lanoxin) is no longer the first-choice medication for the management of AF, but it may be used in patients with heart failure or severe damage to the left side to the heart. Sotalol (Betapace) or amiodarone (Cordarone or Pacerone) may be used for intermediate or long-term treatment of AF after a heart attack. Sotalol is generally the first choice because it has fewer serious side effects than amiodarone.

Bradycardia

Heart attack patients who develop a dangerously slow heartbeat (bradycardia orbradyarrhythmia) are best treated with a pacemaker. When medication is needed, amiodarone (Cordarone or Pacerone) or sotalol (Betapace) may be used.